Apparatus for controlling calenders



y 1970 w. D. BOXMEYER 7 3,521,551

APPARATUS FOR CONTROLLING CALENDERS 7 Sheets-Sheet 2.

Filed March 19, 1968 INVKENTOR ATTORNEY k m m 0 M M, .4 W

July 21, 1970 w. D. BOXMEYER I APPARATUS FOR CONTROLLING CALENDERS '7 Sheets-Sheet 2 Filed March 19, 1968 mvsmon MAA/AMaBaXM EQ wfllfl wu ATTORNEY w. D. BOXMEYER 3,521,551

APPARATUS FOR CONTROLLING CALENDERS '7 Sheets-Sheet 5 BY ATTORNEY 7 V ikw- V 6% \m V w kmmww W A Q W a P M July 21, 1970 Fileci March 19, 1968 July 21, 1970 w. D. BOXMEYER 35 5 APPARATUS FOR CONTROLLING CALENDERS' Filed March 19, 1968 4 7 '7 Sheets-Sheet 4 INVENTOR ML/flMD-BOXMEYE? wwuweh I Y ATTORNEY July 21, 1-970 I w. D. BOXMEYER 3, 5

v APPARATUS FOR CONTROLLING CALENDERS Filed march 19 1968 7 Sheets-Sheet s INVENTOR M44 /flMp-30XMEYK BYW UW ATTORNEY July '21, 1970 A r w. D. BOXMEYER 1,

APPARATUS FOR CONTROLLING CALENDERS Filed March 19, 1968 '7 Sheets-Sheet 6 l i v INVENTOR MZL/flMDBO/YME new ATTORNEY y 1970 w. D. BOXMEYER APPARATUS FOR CONTROLLING CALENDERS 7 Sheets-She et 7 Filed March 19, 1968 \NVENTOR Mum/14D. FOX/WE'VE? "W A). 0%

ATTORNEY 3,521,551 APPARATUS FOR CONTROLLING CALENDERS William D. Boxmeyer, Mahwah, N..I., assignor to Morrison Machine Company, Paterson, NJ. Filed Mar. 19, 1968, Ser. No. 714,306 Int. Cl. 133% 15/14 U.S. Cl. 100-47 15 Claims ABSTRACT OF THE DISCLOSURE A system which is unaffected by changes in Web speed for automatically unloading the nips of a calender to permit the passage of seams, slubs, and the like, hereinafter called seams," in the web through the nips without damage to the calender rolls. The system is provided with a web speed monitor which generates a series of pulses; a first number of such pulses is proportional to the length of travel of the web from the location of the seam detecting heads to the first nip, a second number of such pulses is proportional to the distance through the nips in machines having multiple nips. A Web detector in advance of the calender initiates the counting of the first number of pulses. After the first number of pulses has been counted, mechanism is actuated to unload the calender rolls, thereby permitting the seam on the web to pass safely through the calender. After the second number of pulses has been counted, indicating that the seam has passed through the calender, the mechanism is actuated so as again to load the calender rolls.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to calendering apparatus and, more particularly, to mechanism for automatically unloading the nips of the calender in advance of the passage of a seam, slub, or other zone of increased web thickness on a web therethrough, and for automatically loading the nips of the calender after the seam or slub has passed.

beyond them.

Description of the prior art The nips of calendering apparatus have been previously unloaded and loaded by an operator who is stationed at the apparatus and who watches the web as it travels therethrough. This is, of course, expensive, since it requires the presence of an operator at each calender while it is operating.

The nips of calenders have also been controlled automatically by systems which employ a first set of timers to determine the time lapse between detection of the seam or slub in the web and the unloading of the nip rolls.

Upon nip unloading a second set of timers is energized,

the second set determining the time that the nip rolls remain open. At the completion of the nip open period. the system resets itself to be ready for another operation.

The principal disadvantage of such prior system for automatically controlling the nips of calenders is the fact that the timing period must be varied in length of time each time the speed of the web being processed through the calender is changed. Without definite reference units and a great deal of experience by the operator, this timing period variation often proved to be a very involved operation. Improper setting and environmental factors often caused mis-setting of the system, with resulting damage to the rolls of the calender when the calender nips were not unloaded at the proper time.

SUMMARY OF THE INVENTION The illustrative calendering machine is one having three rolls and two nips; the rolls are constantly resiliently United States Patent "ice urged apart to open the nips, the nips being closed by hydraulic means which overcomes the resilient means. In accordance with the invention, there is provided a speed monitor which is positively driven in synchronism with the web being processed, in the illustrative embodiment the speed monitor being driven by a roll of the calender. The speed monitor generates a succession of electrical pulses or signals of square wave form, the pulses being spaced so that the distance between the peaks of successive pulses is equal to a predetermined distance of web travel.

The output of the speed monitor is connected to a control-logic unit, in which the number of pulses, that is, the distance of web travel is recorded. Electro-magnetic detector heads disposed a predetermined distance in advance of the calender and constituting a seam detector have their outputs connected to the control-logic unit. When the web disturbance, such as a seam or slub in the web, arrives at the seam detector, the seam detector emits an output command to the control-logic unit. Such unit includes a counting and logic circuit connected to produce a first output command after it has received a first predetermined number of pulses from the speed monitor immediately following actuation of the seam detector. The counting and logic circuit also produces a second output command after it has counted a second predetermined number of pulses from the speed monitor, the counting of such second number of pulses beginning with the time of the production of the first output command by the counting and logic circuit. The first predetermined number of pulses corresponds generally to and is a measure of the distance of web travel from the seam detector to the first nip of the calender, and the second predetermined number of pulses corresponds generally to and is a measure of the distance of web travel from the first to the last nip of the calender. It will be understood that provision is made in both the first and second numbers of pulses for the inherent delay or time lag in the unloading of the rolls and thus the opening of the nips, and for the time lag in the loading of the rolls and thus the closing of the nips.

The system is provided with an electromagnetically controlled valve in the hydraulic loading circuit. The control-logic unit is connected to such valve so that the first command emitted by the unit causes the valve to close, thus unloading the rolls, and the second command emitted by the unit causes the valve to open, thereby loading the rolls. At the time of the issuance of the second command, the control-logic unit resets itself and turns off the output from the speed monitor.

The system of the invention may be provided with a fail-safe device which, if the speed-monitor fails to produce an output when the detector heads indicate a seam or slub, will automatically open the nip or nips of the calender and provide an output indication to inform the operator that a malfunction has occurred. The system may also be provided with additional outputs, which issue commands after predetermined lengths of travel of the Web, to control additional functions of the web treating apparatus. The system of the invention has to be set only once. If no physical distances in the web path are altered, the system does not require readjustment when the speed of the web is changed.

BRIEF DESCRIPTION OF THE DRAWINGS The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a somewhat schematic view in perspective of a calender provided with a control system in accordance with the invention;

FIG. 2 is a schematic view illustrating the relationship between the rolls of the calender and the seam detector;

FIG. 3 is a wiring diagram of the circuit of the pulse generator employed in the control system of FIG. 1;

FIG. 4 is a circuit diagram for one of the seam detector heads employed in the control system of FIG. 1;

FIG. 5 is a block diagram of the illustrative control system for the calender;

FIG. 6 is a schematic diagram of a portion of the control system showing the manner of interconnection of the amplifier, the counter units, the reset generator, and the relay driver;

FIG. 7 is a wiring diagram of the initial stage of the first counter 61;

FIG. 8 is a composite wiring diagram of the reset generator and the failsafe circuit;

FIG. 9 is a wiring diagram of the relay driver board and the output control relay; and

FIG. 10 is a partial connection diagram showing the manner of connection between the three units of the counter, the raise and lower gates, and the transistors which receive the output of the amplifier and selectively hold off the respective counter units.

The diagram of FIG. 2 will illustrate generally the problem involved in the operation of a calender, and also serves as an introduction to a description of the manner in which the apparatus of the invention controls the calender. A web 10 travelling to the right toward the calender 11 has a seam 12 in it which requires that the rolls of the calender be separated to permit the seam to pass safely therethrough. Calender 11 has three rolls 14, 15, and 16, the web 10 passing first into nip N between rolls 15, 16, then half-way about roll 15, and finally through nip N between rolls 14, 15, leaving the calender by passing halfway about roll 14 to resume its travel to the right.

Detector heads 17, 19 located a distance L in advance of nip N when energized by seam 12 begin a counting or measuring operation, the apparatus opening the nips N N of the calender just before the seam reaches nip N and closing the nips just after the seam 12 has left nip N Assuming that the counter of the apparatus counts 11 equally spaced pulses in one revolution of the roll 12, the nips of the calender should be separated when the counter has counted a number of pulses, called the rise number, which equals where s is small number of pulses for a safety factor and D is the diameter of roll 14. The nips of the calender should be closed, to secure the maximum output of calendered web, when the counter has counted a higher number of pulses, called the lower number, which equals the rise number L (m X 71 S) plus 2 7r D1 X n s where D equals one-half the circumference of roll 15.

Turning now to the drawings showing the actual construction of the apparatus, the calender 11 is indicated in FIG. 1 as comprising side frames 20 for mounting the three rolls 14, 15, and 16 in bearing housings 21, 22, and 24. Bearing housings 21 are affixed to the frames 20; hearing housings 22 and 24 are slidable vertically on the frames sothat the rolls and 16 may separate from roll 14 and each other under the action of gravity or be moved together by mechanism to be described.

Upper roll 14 has a shaft portion 25 sprocketed to receive a drive chain 26 connected to a motor 27 which drives the calender. Hydraulic cylinders or jacks 29 are positioned beneath bearing housings 24 to raise rolls 15 and 16 to bring the rolls into engagement with one another. As in FIG. 2, the web is illustrated in FIG. 1 as being fed into the nip N between rolls 15 and 16, thence round roll 15 into the nip N between it and roll 14, and then over the latter; as in FIG. 2, a seam or slub in the Web is indicated at 12 approaching the seam detector.

A pulse generator 30 includes a light chopper wheel 31 (FIG. 3) driven in synhronism with roll 14 by a synchronous belt or chain drive 32. Chopper wheel 31 has a plurality of equally spaced holes 33 therein, such holes being located on a circle concentric with the axis of the chopper wheel. In an illustrative embodiment, there are 72 holes 33; each light pulse thus indicates the travel of web 10 through a distance D /72, where as noted, D is the diameter of roll 14. The output of pulse generator 30 is fed from the circuit of the pulse generator in housing 34 over cable 35 to a control-logic unit 36, which will be described below. Unit 36 also receives pulses from detector heads 17, 19 via cable 37. For operating jack cylinders 29, an electromagnetically actuated loading valve 39, having pressure supply and pressure discharge conduits 40 and 41, is connected to cylinders 29 by conduit 42. A relay driver 44 is connected by cable 45 to the output of control-logic unit 36, and relay driver 44 is connected to valve 39 by cable 46.

The control-logic unit 36 is shown in the block diagram of FIG. 5. The inputs for unit 36 are obtained from pulse generator 30 and detector heads 17, 19, such detector heads being connected in series by wire 47 between ground and amplifier 49. The last stage of amplifier 49 is connected to the gate of a silicon controlled switch 50, as shown in FIG. 6. The output of SCS 50, which is mounted on the amplifier board, is connected to a counter including three like units 51, 52, and 53 each having three binary stages in the form of transistor flip-flop circuits. Such counter circuits are shown in Fig. 7.14 on page 197 of General Electric Transistor Manual, 7th edition.

The counter circuits are normally biased to an off condition by circuit means shown more particularly in FIGS. 6 and 9, but when a pulse is generated by the detector heads 17, 19 and supplied to amplifier 49 over cable 54 and by amplifier 49 through SCS (FIG. 6) and cable 55 to each stage of the counters they are turned on. The counters 51-53 are then in a condition to count the pulses supplied by generator 30 over connection 56. Since counters 51-53 are connected in series by leads 57, 59, providing nine series-connected stages, they are capable of counting up to 511 pulses. All stages of counters 51-53 are connected by leads a to 600, 61a to 610, and 62a to 62c to a pair of gating circuits 64 and 65 called a raise gate and a lower gate, respectively. The gating circuits are each set to respond to a desired pulse count and produce output pulses on leads 66 and 67, respectively, when their preset counts are reached. The output of raise gate 64 turns off relay driver unit 44, which includes a relay driver 43, having a connection 69 to a voltage source. When such relay is thus turned 011?, it de-energizes normally energized relay 70 having contacts 71, which then close loading valve 39, and thus enable rolls 15 and 16 to drop, and thus the nips of the calender to open, a predetermined time after detecting heads 17, 19 have sensed a seam in the web.

Lower gate 65 is set to respond to a pulse count which, as previously indicated, corresponds to a time when a web seam has passed the last nip of the rolls, that is, the nip of rolls 14 and 15. Gate 65 then produces a pulse which is conducted by line 67 to reset generator 72 (FIGS. 5 and 8). Reset generator circuit 72 will be described more fully hereinafter. Upon the reception by reset generator 72 of a pulse from gate 65, the reset generator produces an output pulse which is impressed by line 74 on relay driver 43 to turn -'it on again, thereby energizing relay coil 73, opening loading valve 39 and supplying pressure to cylinders 29 to close rolls 14, 15, 16. At the same time a pulse from reset generator 72 is fed over line 75 to amplifier 49 to trigger 011 the SCS 50. When the switch 50 of amplifier 49 is turned off, all stages of counters 51-53 are clamped to ground, and thus the counters are reset to a Zerocount in readiness for the next operation.

The remaining circuit of logic-control unit 36 is failsafe circuit 76 (FIGS. 5 and 8). Its function is to prevent a failure of the rolls to separate in response to the approach of a web seam, due to some equipment failure. The most likely causes of failure are the burning out of the light 77 (FIG. 3) in pulse generator 30,'and the failure of the power supply. Fail-safe circuit 76, therefore, senses the light output of generator 30 via lead 149 and a 9-volt tap of the power supply. If either the light from generator 30 ceases or such voltage source fails, circuit 76 produces an output voltage which turns off relay driver 43 and thus causes the rolls of the calender to separate.

Although the essential construction and function of the units of the system will be familiar to those skilled in the art, for the sake of elucidation some of the units are described further below.

THE PULSE GENERATOR FIG. 3 shows the pulse generator 30 as including the lamp 77, adapted to be connected to a source of power, juxtaposed to the shutter or chopper wheel 31 driven in synchronism with roll 14 as shown in FIG. 1. Wheel 31 has a ring of holes 33 to permit a series of light pulses from light 77 to fall on light responsive transistor 79 which is housed together with the trigger circuit in a cabinet 34 (FIG. 1). Transistor 79 may be, for example, a photo transistor sold by General Electric Co. under the designation L 14A50-2. The collector and emitter of transistor 79 are connected across a small capacitor 80 and its collector is supplied positive voltage from terminal 81 through resistor 82. Transistor 79 is normally off, but conducts when it receives a pulse of light. The voltage across capacitor 80 then falls rapidly to such a level that the transistor 79 cuts off when the light pulse ends, and then capacitor 80 recharges before the next light pulse impinges on the transistor. The output from the collector of transistor 79 is impressed on the base of transistor 84, which together with a second transistor 85 forms a wellknown Schmitt trigger circuit 86 such as that shown in the General Electric Transistor Manual, 7th edition, page 200, Fig. 7.18(A). The output from circuit 86 is a rectangular pulse which is fed to the base of amplifying transistor 87, whose output 89 is connected to the input of counter 51.

THE SEAM DETECTORS Seam detector heads 17 and 19 each includes a variable diiferential transformer as shown in FIG. 4; one such instrument is that made by Appalachian Electronic Instruments, Inc., of Ronceverte, W. Va. Since the heads 17 and 19 are identical, a description of head 17 will suffice. The transformer of head 17 includes a primary winding 89 and a pair of secondary windings 90, 91 connected in series to output terminals 92, 94. The transformer of head 17 includes a movable core 95 connected to yoke 96, having a detector roller 97 thereon. Detector roller 97 rides on web as it passes over guide plate 99. The outputs of secondary windings 90, 91 of head 17 are normally balanced, but when roller 97 is moved by a seam on the web, core 95 moves partly out of the field of one secondary and more fully into the field of the other secondary. The voltage produced by the secondaries of the head 17 are, therefore, changed differentially and a resultant output appears at terminals 92, 94.

As shown in FIG. 5, one of the leads of head 17, for example the terminal 92, is connected to ground, whereas the other lead, terminal 94, is connected by wire 47 to one terminal of the series connected secondary windings of head 19. The secondaries of the two heads are so connected that the outputs from the two heads are in Opposition, that is, displaced 180 in phase. The net voltage induced in the secondaries of the two heads is zero when no seam or slub is passing under either detector head. Any displacement of the roller at either detector head unbalances one head with respect to the other, and thus produces a voltage input to the amplifier 49. Such series opposition connection of the secondaries of the two heads balances out voltages produced by environmental or operational conditions which simultaneously vary the outputs of the detector heads 17, 19, but voltages produced by either head in response to a seam or slub will not be balanced out. Thus false opening and closing of rolls 14, 15, and 16 are obviated. The first pulse supplied by a detector head, usually head 17, turns on amplifier 49, which once turned on stays on until turned off by reset generator 72 as already described, and hence the output from the second detector head 19 has no effect on amplifier 49, since the last stage of such amplifier is the silicon controlled switch 50.

THE COUNTER Counter units 5153 can be formed of any suitable binary circuit of which many types are in use. Each counter consists of three gated fiip-flop circuits followed by an output amplifier. The first stage 100 of unit 51 is shown in FIG. 7; the other two stages (not shown) of such unit are identical with it. The input pulses are supplied by pulse generator 30 to counter stage 100 over lead 56. The collectors of the two transistors 101, 102 of each stage are connected to a positive voltage by lead 104 and the bases of such transistors are connected to a negative voltage supply by lead 105. Each collector is connected to the base of the other transistor 101, 102 to form a fast acting flip-flop.

The output from stage 100 of counter unit 51 is supplied to the next stage (not shown) by a wire 106. The lead wire 60a from stage 100- to raise gate 64 is connected to the collector of transistor 102 through a resistor and a diode as shown in FIGS. 7 and 10. The collector of transistor 102 is also connected, through a diode which is polarized reversely from that in lead 60a, by a wire 107 to the collector of a transistor 109. The emitter of transistor 109 is grounded, and the base thereof is connected through a high resistance 110 to the wire 55 connected to the anode of SCS 50, as shown in FIGS. 6 and 10. There are provided two further transistors 111 and 112 similar to transistor 109', the bases of transistors 111 and 112 being connected in parallel with the base of transistor 109, transistors 111 and 112 being connected similarly to transistor 109 and having their collectors 114 and 115 connected to the first stage of the respective counter unit '52 and 53 in the same manner that the collector of transistor 109 is connected to stage 100 of the first unit 51 of the counter.

The counter functions as follows: The NPN transistor 101 of the first flip-flop stage 100 of counter unit 51 is held 011 while the NPN transistor 102 of such stage is held on through the biasing diodes in such stage and the transistor 109 (FIGS. 6 and 10) on the amplifier board. The input signal from the pulse generator 30 is continuously applied through the wire 56 to the first stage 100 of the counter; if the right side of the flip-flop stage 100 were not clamped toa ground potential, the flip-flop would operate in a bistable mode, switching each time a pulse appeared at the input wire 56. However, the right side of the flip-flop is clamped to ground through the diodes and the transistor 109 on the amplifier board; thus such right side cannot rise above ground potential and the flip-flop will not shift. When the right side clamp is 7 removed by the turning off of the transistor 109 by the SCS 50 on the last stage of the amplifier (FIG. 6), the flip-flop responds to the input pulses from the pulse generator.

Each counter unit 51-53 is provided with a respective set of diodes 116a-116e in its output circuit (FIG. 10). When the preset number on the raise gate 64 is reached, the correct raise diodes of the diode set are reverse biased and the voltage will rise at the cathode trigger 120' of the SCS 119 on the relay driver board (FIG. 9) through wire 121 causing such SCS to turn on and to deenergize the coil 73 of the relay coil 70. The control relay 70' will remain in the deenergized position until the number set on the lower gate 65 is reached by the counters. At this time the reset generator 72 (FIG. 8) is triggered by a positive pulse from the lower gate through wire 67, thereby causing the entire circuitry to be readied for another operation.

DHE RELAY DRIVER As shown in FIG. 9, the upper terminal of a reset switch 122 is connected by a wire 124 to the collector of a PNP transistor 125. The emitter of transistor 125 is connected through a wire 126 to the plus terminal of a source of direct current. The base of transistor 125 is connected through a resistor to the wire 74 which leads to the reset generator (FIG. 8). The lower terminal of the reset switch 122 is connected through a wire 129 and through a resistor 130 to the anode of the SCS 119. Also connected to the lower contact of the reset switch 122 is a wire 131. As shown in FIG. 6, wire 131, which is connected to the anode of SCS 50, has a resistor 132 interposed therein. The above-mentioned wire 55, leading to the bases of the transistors 10 9, 111, and 112, is connected to wire 131 between the resistor 132 and the anode of the SCS 50. The anode of SCS 119 (FIG. 9) is connected through a diode and a resistor to a wire 133 which leads to the reset generator, as shown in FIGS. 8 and 9. An NPN transistor 134 has its collector connected to the trigger gate 120 of SCS 119, and its emitter connected to ground. The base of transistor 134 is connected by a wire 127 having a resistor of large value therein to the cathode of a diode 123, the anode of which is connected to the wire 74 leading to the reset generator.

An NPN transistor 135 has its base connected to a wire 133 leading to the reset generator (FIG. 8). The collector of transistor 135 is connected to the Wire 129 leading to the anode of SCS 119. The emitter of transistor 135 is connected through a resistor to the base of a further NPN transistor 136, the emitter of which is connected to ground through a resistor. The base of transistor 135 is connected at 13-9 to the negative terminal of a source of direct current, terminal 139 being, for example, at a potential of -9 volts. The collector of transistor 136 is connected to one end of the coil 73 of the relay 70, the other end of the relay coil being connected to the positive terminal 69 of a source of direct current for energizing such coil. Coil 73 is shunted by a resistor and a diode, the resistor 69' being connected to terminal 69 and the cathode of the diode being connected to the resistor, as shown. Relay 70 has contacts 71 (FIG. which control a further, power relay (not shown) which energizes the loading valve 39.

It will be seen that when transistor 135- is on it causes transistor 136 to be on, and that when the latter transistor is on it energizes coil 73 of relay 70*. Normally conducting transistor 125, in turn, causes transistor 135 to be on.

The relay driver functions as follows: The system is placed in operative condition when the reset switch 122 is closed. Under normal operating conditions, that is, with no seam in the web immediately approaching the calender, the transistors 125, 135, and 136 are on, the SOS 119 is off, and the transistor 134 is off. When a seam 12 on the web energizes the detector head 17, there is produced a positive pulse, as above described, from the raise gate 64, such pulse turning the SCS 119 on by its trigger cathode gate This causes the transistor pair and 136 to turn off, thus deenergizing the control relay 70. The SCS 119 remains conducting unless the reset switch 122 is opened, or the SCS 119 is reset.

To reset the SCS 119, a pulse from the reset generator is applied to the base of the transistor 125 causing it to turn oil. This in turn breaks the positive DC voltage tothe SCS 119 causing it to turn olf and to reset itself. At the same time that the SCS 119 is turning off, the transistor 134 is turned on. This serves to bypass any signal from the raise gate 64 which would otherwise tend to cause false output signals. When the SCS 119 is reset, the transistor '134 is turned back off, and the system is ready for the next operation.

THE RESET GENERATOR This circuit, combined with the failsafe circuit, is shown in FIG. 8, the portion thereof to the left of the broken vertical line, designated 72, being the reset generator and that to the right of such line, designated 76, being the failsafe circuit. Both circuits are connected through a wire 144 to the positive terminal of a source of direct current, the output end of the failsafe circuit being connected through a wire 145 to the negative terminal (-9 volts, for example) of a direct current source. The reset generator 72 includes a portion generally designated 151 which includes two similar NPN transistors 152, 154, connected in a flip-flop circuit, and a unijunction transistor 155 connected to form a monostable vibrator. Wire 67 connected to the lower gate 65 is connected through a large resistance and a small capacitor to the base of an NPN transistor 150, the collector of which is connected to the collector of transistor 152. The emitter 156 of unijunction transistor 155 is connected through a large resistance and a diode 160 to one terminal of a small capacitor 159, the other terminal of such capacitor being connected to the B terminal 157 of the unijunction transistor 155.

Terminal 157 is also connected to the voltage source 144, as shown. The B terminal 161 of the unijunction transistor is connected through a small resistor to ground. The collector of transistor is connected to the voltage source 144 to the emitter of transistor 162. The collector of transistor 162 is directly connected to wire 74 which leads to the relay driver (FIG. 9) and through a diode and a resistor to the wire 133 which also extends to the relay driver.

The reset generator functions as follows: When the reset switch 122 is closed and the system is operating normally with no seam in the web immediately approaching the calendar, the transistors 150 and 152 are normally non-conducting and the transistor 154 is normally conducting. The unijunction transistor 155 has no voltage at its emitter and is therefore off, and the right side of the capacitor 159 is positive. The transistor 162 is held non-conducting by the reverse biasing due to the non-conducting left side of the flip-flop.

When a seam 12 on a Web 10 has actuated the detector head 17, a positive pulse is received from the lower gate 65 through the wire 67. This causes transistor 150 to turn on, and the flip-flop including the transistors 152, 154 to be pulsed. This causes the transistor 152 to turn on and the transistor 154 to turn 011. When the flip-flop shifts as described above, the transistor 162 turns on, thus causing a voltage to appear in wire 74 and to be transmitted to the base of transistor 125 on the relay driver board to turn transistor 125 off. At the same time that the transistor 162 is on, a voltage appears at the emitter 156 of the unijunction transistor 155. When this voltage reaches its peak value, the unijunction transistor fires, causing a pulse which is negative with respect to the positive voltage on wire 144 to appear at the B terminal 157 of the unijunction transistor. This negative pulse is communicated through the capacitor 159 causing the flip-flop of the vibrator 151 to shift back to its original condition.

THE FAILSAFE CIRCUIT This circuit, which is generally designated 76 in FIG. 8, provides for the automatic opening of the rolls of the calender if either the light bulb 77 or the negative voltage source of the system, to which wire v145 is connected, should fail. As indicated in FIG. 3, the light bulb 77 of the pulse generator is energized from a direct current source having a positive terminal 146 and a negative terminal 147. A tap 159 is taken from the terminal .147 beyond the light bulb 77, wire 149 being connected to the base of an NPN transistor 164 in the failsafe circuit. Under normal operating conditions with current flowing through the filament and such transistor is confiowing through the filament of light 77, the base of transistor 164 is positive and such transistor is conductive. The collector of transistor 164 is connected to the positive terminal 144 of the direct current source and through a large resistance and a diode to the base of an NPN transistor 165, the emitter of which is connected to ground and the collector of which is connected through a diode to the wire 133 which extends to the relay driver board (FIG. 9). There is provided a further NPN transistor 166, the base of which is connected through a large resistance to the wire 145 connected to the -9 volt terminal; the emitter of transistor 166 is connected through a resistance to ground, and the collector of transistor 166 is connected to the collector of transistor 164 through a resistance.

The failsafe circuit operates as follows: When the system is normally operative and no seam 12 is immediately approaching the calender, and with the light 77 in operative condition, the transistor 164 is conductive, the transistor 165 is non-conductive, and the transistor 166 is non-conductive.

Should the signal light 77 fail, the transistor 164 turns off. This causes the transistor 165 to turn on and through wire 133 to shunt the base of the transistor 135 in the relay driver board (FIG. 9) to turn such transistor 135 off. This turns off the transistor 136 on the relay driver board and thus deenergizes the coil 73 of the relay 70.

Should the --9 volts (wire 145) supply fail, the transistor 166 in the failsafe circuit 76 will turn on. This in turn will cause the transistor 165 to become conductive and to deenergize the control relay 70 in the same manner, described above, as when the light source fails. When the transistor 125 on the relay drive board turns oil due to the reception of a reset pulse from lower gate 65 through the wire 67, it turns off the two SCSs, that is, SCS 119 located on the relay driver board and SCS 50 on the amplifier board. The turning off of SCS 50 causes the counter circuitry to be reset to in readiness for the next operation.

The raise gate 64, the lower gate 65, and their manners of connection to the units 51, 52, and 53 of the counter are shown more completely in FIG. 10. As there shown, the raise gate 64 has an input terminal block 64a and a similar output terminal block 64b, the terminals of the two blocks being selectively connected by jumper Wires (shown in curved dash lines) which are installed so as to energize the relay driver through wire 66 only when the counter has counted a predetermined rise number. The lower gate 65 similarly has an input terminal block 65a and an output terminal block 65b. Blocks 65a and 65b are selectively connected by jumper wires which are installed so as to energize the relay driver 43 through wire 67 to the reset generator 72 and thence through wire 74 to the relay driver only when the counter has counted a predetermined lower number."

I claim:

1. In a calender for a travelling web, said calender having at least two opposed rollers selectively cooperating to form a nip therebetween, and roll pass controlling means selectively to thrust the rolls toward each other into operative engagement with the web and to separate the rolls, the improvement which comprises means for detecting a localized zone of substantial increase in the thickness of the web disposed to cooperate with the travelling web at a predetermined distance upstream of the calender, said zone detecting means emitting an electrical signal when said zone of the web encounters it, means responsive to operation of the detecting means comprising web travel measuring means including an electronic digital computer, means connecting the detecting means to the computer so as to initiate operation of the computer upon the reception by the computer of a signal from the detecting means, and means operated by the computer after it has measured a predetermined length of travel of the web for operating the roll separating means, whereby the rolls are separated when said zone of the web closely approaches the nip between the rolls.

2. A calender as claimed in claim 1, comprising a source of voltage for energizing said measuring means, and means responsive to a predetermined failure of voltage of said source to separate the rolls of the calender.

3. A calender as claimed in claim 1, wherein the measuring means includes means which is driven in synchronism with the travelling web and which generates uniformly spaced electrical pulses of energy, and circuit means feeding said pulses to the digital computer.

4. A calender as claimed in claim 3, wherein said pulse generating means comprises a source of light, a light sensitive means adapted to receive light from the light source, and a shutter interposed between the light source and the light sensitive means and driven in synchronism with said roll of the calender, said shutter being so constructed and arranged as to interrupt the light falling upon the light sensitive means at intervals corresponding to uniform angles of turning of the said roll.

5. A calender as claimed in claim 4, comprising means operative upon the failure of the source of light of the pulse generator to separate the rolls of the calender.

6. A calender as claimed in claim 3, wherein the roll separating means is operated by the computer after the computer has received a first predetermined number of electrical pulses of energy.

7. A calender as claimed in claim 6, comprising means to terminate the operation of the digital computer after it has received a second predetermined number of pulses signifying that said zone of the web has passed the last nip of the calender, and means responsive to the last named means for operating the roll pass controlling means to thrust the rolls toward each other into operative engagement with the web.

8. A calender as claimed in claim 7, wherein the pulse generating means produces said pulses at all times when the web is travelling, the means for detecting a localized zone of substantial increase in the thickness of the web comprises two web calipering devices disposed one in advance of the other along the path of travel of the web, said calipering devices having differentially connected coils, a source of a fixed reference voltage connected in opposition to the differentially connected coils, and means for initiating the operation of the computer when the voltage which results from the diiferentially connected coils and the source of reference voltage attains a predetermined value.

9. A calender as claimed in claim 6, comprising means automatically operable upon the termination of the operation of the counter after it has received said second predetermined number of pulses to reset the counter to its initial condition.

10. A calender as claimed in claim 9, comprising means automatically operable upon the termination of the operation of the counter after it has received said second predetermined number of pulses effectively to disconnect the pulse generating means from the counter.

11. In a system handling a travelling web, said system having an apparatus operative upon the web, and means controlling the apparatus, the improvement which comprises means for detecting a localized zone of substantial increase in the thickness of the Web disposed to cooperate with the travelling web at a predetermined distance upstream of the apparatus, said zone detecting means emitting an electrical signal when said zone of the web encounters it, means responsive to operation of the detecting means comprising web travel measuring means including an electronic digital computer, means connecting the detecting means to the computer so as to initiate operation of the computer upon the reception by the computer of a signal from the detecting means, and means operated by the computer after it has measured a predetermined length of travel of the web for operating the means controlling the apparatus.

12. A system as claimed in claim 11, wherein the measuring means includes means which is driven in synchronism with the travelling web and which generates uniformly spaced electrical pulses of energy, and circuit means feeding said pulses to the digital computer.

13. A system as claimed in claim 12, wherein the controllable means is operated by the computer after the computer has received a first predetermined number of electrical pulses of energy.

14. A system as claimed in claim 13, comprising means to terminate the operation of the digital computer after it has received a second predetermined number of pulses signifying that said zone of the Web has passed the ap- 12 paratus, and means responsive to the last named means for operating the controllable means.

15'. A system as claimed in claim 14, wherein the pulse generating means produces said pulses at all times when the web is travelling, and means for detecting a localized zone of substantial increase in the thickness of the Web comprises two web calipering devices disposed one in advance of the other along the path of travel of the web, said calipering devices having differentially connected coils, a source of a fixed reference voltage connected in opposition to the differentially connected coils, and means for initiating the operation of the computer when the voltage which results from the differentially connected coils and the source of reference voltage attains a predetermined value.

References Cited UNITED STATES PATENTS 3,380,431 4/1968 Keges et al. 118-8 3,126,564 3/1964 Elliott 15102 3,380,431 4/1968 Keges et al 118-8 FOREIGN PATENTS 144,015 2/1954 Sweden. 1,024,796 4/1966 Great Britain.

WALTER A. SCHEEL, Primary Examiner L. G. MACHLIN, Assistant Examiner U.S. Cl. X.R. 1 18-8 

